A laser utilizing ion source generates plasma through irradiating the condensed laser beam to a solid target and then evaporates and ionizes the element of the target by the laser energy. The generated plasma maintain their state and are transported to the entrance of an accelerator, where only ions are input to the accelerator by differential electric potential and then outputted as the ion beam (refer to Patent document 1, 2). While it is known that the ion acceleration of the accelerator is superior if the valence of the positive ion is higher or the mass thereof is smaller. Also the laser utilizing ion source is effective in generating a polyvalent positive ion.